To form a pipe line, pipe sections (sometimes for convenience referred to herein simply as "pipe") are welded together. The welding operation must be conducted in relatively dry conditions; otherwise oxygen present in the water at the welding site will tend to enter the weld spot, thereby weakening the weld.
When the welding is done in the summer months or in areas of favourable client, any accumulated rainwater can normally be fairly readily drained out of a pipe section and the pipe section welded in place without a serious problem, but in the winter months, especially in colder climates, there is a tendency for snow to blow into pipe sections and accumulate; sometimes a person has to enter the pipe section with a broom and sweep it out in order to get rid of the snow. It is therefore desirable to have a weather protector at each end of a pipe section to prevent snow in particular and also rain and debris from blowing into the pipe section and accumulating there.
It is, of course, easy enough to provide a weather protector--one could simply take plastic sheeting, wrap it around the end of the pipe section, and tie a string around the end of the pipe section to hold the sheeting in place. More elegant solutions than this to the problem have been proposed in the past. Among them are the following:
Vestal in U.S. Pat. No. 3,744,528 issued 10 Jul., 1973 discloses a pipe-end protector comprising a double-wall sleeve that fits over the end of the pipe and terminates in the interior of the pipe, recessed from the pipe-end, in a circular barrier. This type of pipe-end weather protector is completely satisfactory to its purpose of keeping snow, rain and debris out of the pipe. However, it suffers from the significant disadvantage that when the pipe is handled from time to time (stacking in a storage yard; loading onto a transport vehicle; unloading from the transport vehicle; moving from a depository to the site at which it is to be welded, etc.) the weather protector may be damaged or dislodged. The reason for this is that pipe-gripping machinery typically includes a gripping element that grips the pipe section at its end. This gripping element therefore can easily damage Vestal's closure element and may dislodge it. Vestal proposes also that his weather protector be made of plastic, which is not readily biodegradable. Further, Vestal relies upon some flexibility of the plastic barrier portion of his weather protector to move like a diaphragm to accommodate pressure differentials between the interior and exterior of the pipe section. This may not be sufficient to accommodate sudden pressure changes; the plastic could burst.
Mallard in U.S. Pat. No. 3,078,879 issued 26 Feb., 1963 discloses a weather protector for a pipe end that is insertable into the pipe end and may remain in place inset from the pipe end so that pipe gripping tools do not come into contact with the weather protector. Mallard thus avoids a significant disadvantage in the Vestal design. However, because there is no portion of the Mallard weather protector that extends outwardly to the edge of the pipe, it is difficult to place the weather protector in the proper place within the pipe and equally difficult to dislodge it and remove it prior to welding. Further, Mallard, in order to maintain the weather protector in gripping contact with the interior walls of the pipe, relies upon a separate band and requires a special tool to install the weather protector and the band in place within the pipe section. So Mallard's design is both awkward to use and expensive. Mallard also proposes the use of polyethylene plastic for use as the material of which the weather protector is manufactured, giving rise to the same problem of poor biodegradability from which Vestal also suffered. Polyethylene may also become unsatisfactorily brittle in very cold weather.
Even more elaborate and expensive pipe-end closures have been devised such as those illustrated in U.S. Pat. No. 2,737,205 (Stringfield - 6 Mar., 1956); U.S. Pat. No. 5,074,336 (Black - 24 Dec., 1991); U.S. Pat. No. 4,957,141 (Dreyfuss - 18 Sep., 1990) and U.S. Pat. No. 4,915,137 (Hall - 10 Apr., 1990). All of these present complex and expensive structures that suffer from some or all of the disadvantages mentioned previously. None is conveniently usable in conjunction with conventional pipe-end gripping tools.